Effect of austempering temperature on microstructure and mechanical properties of ADI

ADI (Austempered Ductile Cast Iron) has emerged as a major engineering material in recent years because of its excellent mechanical properties. In the present work, a low manganese nodular cast iron with predominantly pearlitic as-cast structure was processed by a unique austempering process. The specimens were austempered at 300 and 320 degree C for 1 hour after austenitizing at 900 degree C for 1 hour resulted in microstructure consisting ausferrite, a combination of acicular ferrite and stabilized austenite. Microstructural development has been studied using light optical microscope and scanning electron microscope. Mechanical properties such as ultimate tensile strength, toughness, percentage elongation and hardness have also been measured. A 43% and 25% increase in ultimate tensile strength and hardness were measured respectively, where as, a substantial reduction (77%) in percentage elongation was measured and a nominal (1.1 %) increment in toughness was observed. (author)